Method of hydrolyzing ethylenesulfuric acid absorbate



May 14, 1957 w. c. MULLER ETAL 2,792,433

METHOD OF HYDROLYZING ETHYLENE-SULFURIC ACID ABSORBATE Filed Oct. 20, 1955 CONDENSER COOLER INVENTOR ATTORNEY METHOD OF HYDROLYZIN G ETHYLENE- SULFURIC ACID ABSORBATE Werner C. Muller, Roslyn, and John S. Atwood, Port Washington, N. Y., assignorsto National Fctro-Chemrcals Corporation, a corporation of Delaware Application October 20, 1953, Serial No. 337,268

Claims. (Cl. 260-639) This invention is a new and useful method of hydrolyzing ethylene-sulfuric acid absorbate. This application is a continuation-in-part of our prior application, Serial No. 286,752 filed May 8, 1952, and now abandoned.

In accepted commercial practice the hydrocarbon raw material for the manufacture of such 'absorbate is formed by cracking a petroleum distillate or natural gas followed by rectification of the cracked product to produce a cut, the olefin content of which is predominantly ethylene. This cut is then absorbed countercurrently in strong sulfuric acid under a pressure of at least 200 lbs. p. s. i. g. to produce an absorbate containing both monoand diethyl sulfates and preferably the ethylene content of which ranges from 1.3 to 1.5 mols of ethylene per mol of sulfuric acid.

Our invention is particularly directed to the hydrolysis of such absorbates. The invention will be fully understood from the following description read in conjunction with the drawing, which is a diagrammatic showing of apparatus in which the invention may be carried out.

Referring to the drawing 1 designates a liquid-vapor countercurrent contacting device of the type generally termed a rectification tower. The invention is of course not limited to use with a rectification type tower since any liquid-vapor countercurrent contacting device, such as a packed column or sieve-tray column, may be similarly employed. Device 1 consists of a vertical tower spanned by a number of horizontal trays 2, each carrying downfiow pipes 3 and devices, such as hell caps 4, for dispersing ascending vapor into the pool of liquid retained on each such tray. Absorbate, preferably at a temperature between 160 and 220 F. of the type referred to, is introduced into the mid-section or upper half of such device through pipe 5 controlled by valve 6. Water, preferably at a temperature between 160 and 220 F. for hydrolysis, is introduced into the upper section of such device through pipe 7 controlled by valve 8. The water moves downwardly from tray to tray in the upper part of the device, comingling with the absorbate on the tray at which the absorbate is introduced. If a packed column or sieve-tray column is used, this will occur at the level at which the absorbate is introduced. The amount of water so introduced is sufficient to dilute the sulfuric acid present to from 3565 weight percent (hydrocarbon-free basis.) Steam is introduced into the base 9 of the device through pipe 11 controlled by valve 12. Liquid may be withdrawn from the base of the device by pipe 13 which projects upwardly within the base 9 of the device to retain a pool 14 of liquid. The amount of heat introduced through pipe 11 is sufficient to maintain this liquid in a state of active boiling with the production of vapors which ascend from plate to plate or from level to level within the device 1. Below the point of introduction of the absorbate, hydrolysis proceeds to completion as a result of heat transfer upwardly within the device 1 from the liquid 14, as a result of ascending vapors. The rate of introduction of the absorbate is coordinated with the heat input, with the result that hydrolysis is complete by the time the lower end of the device is reached and the material flowing downwardly within the device .is simultaneously denuded of its ethanol content, with the result that the liquid in the base of the device is dilute aqueous sulfuric acid of from 35-65 weight percent (hydrocarbon-free basis). Inasmuch as the system is operated at temperatures above the boiling point of ethanol, the ethanol as produced, passes immediately into vapor phase, moving upwardly in device 1 and passing out of this device through pipe 15 into condenser 16, by which it is condensed into the liquid phase. The liquid ethanol passes out of the condenser 16 through pipe 17 and 'by manipulation of valve 18, a part of it is passed to cooler 19 and thence through pipe 21 out of the system for utilization elsewhere. A part of the ethanol passing downwardly through pipe 17 is passed through pipe 22 controlled by valve 23 back into the upper end of device 1. The amount recycled through pipe 22 in this way is .suflicient to 'keep the overhead passing off through pipe 15 a approximately 60 mol percent ethanol.

In accordance with our invention the dilute aqueous sulfuric acid withdrawn from base 9 of device .1 through pipe 13 is forced by pump 24 into pipe 25, from which a part of it is withdrawn for concentration and reuse through pipe 26 controlled by valve 27. A part of it is, however, returned through pipe 28 controlled by valve 29 into the upper end of device 1 at a point not lower than and preferably above the point of introduction of the absorbate and preferably at a point below the point of introduction of the water hereinabove referred to. recycled acid is preferably at a temperature between and 220 F. and is held within these limits by means of a cooler diagrammatically indicated by 31. Based on the actual water content of this recycled acid, the amount so recycled will range from 10% by weight of the water introduced through pipe 7 up to 300%, and preferably is between 25 and 200 weight percent of the water introduced through pipe 7.

Within these recycle ratios the heat into the base of the tower and the amount of reflux returned through pipe 22 are adjusted to maintain from 1040 mol percent ethanol (sulfate-free basis) on the trays or at the levels between the points at which pipes 28 and 5 enter the device 1, and from 20-60 mol percent ethanol (sulfatefree basis) on the trays or at the levels between the points at which pipes 7 and 28 enter device 1. Sulfate-free basis means the exclusion, for purposes of calculation, of hydrogen sulfate H2804 as well as mono and dialkyl sulfates.

The following is a practical example of the operation of our process. The apparatus corresponds in design to that shown in the drawing. The absorbate is derived from the countercurrent contacting of ethylene with strong sulfuric acid in an absorption tower under pressures of approximately 250 lbs. per square inch. This absorbate contains approximately 1.38 mols of ethylene per mol of sulfuric acid. The absorbate is fed in at point 5 at a rate sufiicient to introduce one mol of H2804v carrying 1.38 mols of ethylene per hour. The amount of dilution water fed in at point 7 is 3.0 mols of H20 per hour. The amount of steam fed in at point 11 is 4.58 mols of H20 per hour, and the temperature obtaining in the base is approximately 266 F. The amount of spent acid diverted from the system through the pipe indicated by 26 is 5.44 mols of H20 per hour containing 1 mol of H2804, i. e., a total of 6.44 mols and a concentration of 50 weight percent H2804. The amount of acid recycled into the device at 28 is 1.70 mols of H20 containing 0.31 mol of H2804, i. e., a total of 2.01 mols. The average concentration of ethanol within the device between the points at which pipes 5 and 28 enter is 13.7 mol percent This ethanol. The average concentration of ethanol in the device between the points at which pipes 7 and 28 enter containing both monoand a substantial amount of di- .ethyl-sulfates, which comprises introducing such an absorbate into a vertical liquid-vapor countercurrent contacting device, introducing water at a point above the point of introduction of such absorbate in amount suflicient to dilute the sulfuric acid present to a concentration of from 35-65 weight percent (hydrocarbon-free basis),

introducing heat into the lower section of the device sufiicient to maintain boiling in the base of such device and a temperature above the base at which hydrolysis proceeds actively and the ethanol produced by the hydrolysis moves upwardly in vapor phase, withdrawing an ethanol-containing stream from the upper end of said device, condensing and returning part of said ethanol into the upper end of said device, conducting away the remainder of said ethanol as a product of said hydrolysis,

continuously withdrawing dilute aqueous sulfuric acid from the lower end of said device and recycling part of such acid without substantial reconcentration into the upper end of said device at a point not lower than the point of introduction of such absorbate.

2. Process according to claim 1 in which such re cycled acid is introduced me point above the point of introduction of such absorbate.

3. Process according to claim 1 in which the amount of such recycled acidis sufficient to return to said device from l0300 weight percent of the said dilution water.

4. Process according to claim 1 in which the amount of such recycled acid is suflicient to return to said device from 25-200 weight percent of the said dilution Water.

5. Process according to claim 1 in which the ethanol returned to the upper end of said device is in an amount sufiieient to maintain a concentration of from 20-60 mol percent ethanol in the upper end of said device.

References'Cited in the file of this patent UNITED STATES PATENTS 2,530,953' Fuqua Nov. 21, 1950 2,629,747 Fuqua Feb. 24, 1953 FOREIGN PATENTS 493,724 Canada June 16, 1953 

1. A CONTINUOUS SINGLE STAGE PROCESS FOR SUBSTANTIALLY COMPLETELY HYDROLYZING ETHYLENE-SULFURIC ACID ABSORBATE CONTAINING BOTH MONO- AND A SUBSTANTIAL AMOUNT OF DIETHYL-SULFATES, WHICH COMPRISES INTRODUCING SUCH AN ABSORBATE INTO A VERTICAL LIQUID-VAPOR COUNTERCURRENT CONTACTING DEVICE, INTRODUCING WATER AT A POINT ABOVE THE POINT OF INTRODUCTION OF SUCH ABSORBATE IN AMOUNT SUFFICIENT TO DILUTE THE SULFURIC ACID PRESENT TO A CONCENTRATION OF FROM 35-65 WEIGHT PERCENT (HYDROCARBON-FREE BASIS), INTRODUCING HEAT INTO THE LOWER SECTION OF THE DEVICE SUFFICIENT TO MAINTAIN BOILING IN THE BASE OF SUCH DEVICE AND A TEMPERATURE ABOVE THE BASE AT WHICH HYDROLYSIS PROCEEDS ACTIVELY AND THE ETHANOL PRODUCED BY THE HYDROLYSIS MOVES UPWARDLY IN VAPOR PHASE, WITHDRAWING 